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ELECTROMAGNETIC
COMPATIBILITY
Dr. Donald Church
Senior Staff Engineer
International Rectifier Automotive Systems
November 17, 2005
Electromagnetic Compatibility
Outline
• Introduction: Terms & Definitions
• EMC in Product Development: Activities & Outputs
• EMC in the Automotive Environment: Challenges
• Example: Electro-Hydraulic Power Steering System
• EMC and the IEEE: Education
• Questions
ELECTROMAGNETIC COMPATIBILITY
(EMC)
1. Electromagnetic Emissions
Your System Cannot Interfere With Other
Systems or Subsystems in the Vehicle
(e.g., FM Radio).
2. Electromagnetic Susceptibility
Your System Must Continue to Operate Correctly
in the Presence of Interference From Others or
Transient Disturbances.
ELECTROMAGNETIC INTERFERENCE
(EMI)
• Conducted Interference
Enters/Exits on Wires for Power or Control
• Radiated Interference
Enters/Exits Through the Air
Emissions Must be Controlled to Protect:
AM & FM Radio Stations
Aircraft Communications & Navigation
Emergency Services Land Communications
EMI MEASUREMENT
Spectrum Analyzer Screen
Units: dBuV
50dBuV = 316uV
~15uV
Frequency
100kHz – 100MHz
EMC in Product Development
Typical Development Cycle Outputs
Corresponding EMC Outputs
• Product Specification
• EMC Requirements Analysis
• System Architecture
• EMC Concept Review
• Physical Design
• EMC Design Review
• Product Qualification
• EMC Lessons Learned
EMC in Product Development
Typical EMC Activities During Product Development
Specification:
Define the EMC requirements (5 types).
Which directives apply?
Ensure the standards are understood.
What are the implications?
Architectural/System Design:
Propose preliminary EMC design concepts.
Create the EMC test plan.
Propose PCB design strategies.
Review Power Stage Concept for EMC.
Do an EMC risk analysis.
Detailed Design:
Implement the strategies and concepts.
Do pre-screening tests and simulation.
Prototype/Qualification:
Do formal certification testing.
Re-design & Re-test?
Failures here are expensive!
EMC In The Automotive Environment
• Harsh Environment
Power Line Transients
RF Interference
Electrostatic Discharge
Power Line Electric & Magnetic Fields
• High Reliability
1 ppm Goal
“Fail Safe” is Critical
• Extreme Cost Sensitivity
EMC In The Automotive Environment:
Susceptibility
Power Transients
Inductive Load Switching
Voltage Sag
“Load Dump”
RF Immunity
On-Board Transmitters
Radio Stations
Airport Radar Systems
Sensors are Most Vulnerable
Electrostatic Discharge (ESD)
Up to 15kV
EMC In The Automotive Environment:
Emissions
Radiated Emissions
Very Sensitive Receivers
Distance to the Antenna
50dB Lower Than Commercial Limits
Cables Are Unintended Antennas
PCB Traces Also Radiate
Digital Circuits Are The Main Source
EMI Lesson #1: Remember Fourier!
The Energy in a Trapezoidal Waveform is a Function of the Pulse
Width and the Rise and Fall Times.
Example: 20kHz waveform with 10ns rise & fall times.
F1 ~ 13kHz
F2 ~ 32MHz
ELECTRO-HYDRAULIC
POWER STEERING SYSTEM
Hydraulic Pump
Electronic Control Unit
• Three-Phase Inverter
• Microcontroller & S/W
• Sensors
• CAN Bus
Three-Phase Brushless
DC Motor
Conducted Emissions Results
Test Conditions; Typical Load, PWM @ 20-30A, 1,000RPM
PWM
Harmonics
Power Stage
& I/O
Load Z
Low Frequency; 150kHz - 30MHz
Fast Edges & I/O
High Frequency; 30MHz – 100MHz
EMC AND THE IEEE
• Ancora Imparo – “I Am Still Learning”
Michelangelo at Age 87
• IEEE EMC Society
• IEEE Annual EMC Symposium
• NARTE & The IEEE EMC Society
Fostering and promoting Technical Awareness,
Education and Achievement in EMC
EMC Summary
• What it is and why it is important
• Designing Early for EMC
• EMC Challenges in the Automotive Environment
• Example of a Certified Automotive Component
• Continuing Education Through NARTE & IEEE
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